This invention relates generally to the field of flywheels or rotors used in internal combustion engines having magneto ignition systems. More specifically, the invention relates to a improvements in such magneto rotors that provide substantial weight reductions, thereby yielding enhanced engine performance.
Conventional magneto rotors, used in small internal combustion engines (of the type found in vehicles such as jet skis), comprise a substantially annular body having a closed end and an open end. A sleeve for the engine crank shaft extends axially through the center of the rotor from the closed end to the open end. The annular peripheral wall of the rotor is coaxial with the central sleeve, defining an annular inner peripheral surface, facing the sleeve, to which a plurality of magnets are attached. The magnets typically are fabricated of magnetized steel or ceramic. The magnets are typically attached to the inner peripheral surface of the rotor by rivets or an adhesive, or both.
The steel or ceramic magnets used in the prior art rotors are relatively massive, necessitating a rotor that is, likewise, relatively massive. Thus, such rotors are typically fabricated of a steel alloy to achieve the needed levels of structural strength and rigidity.
As can be appreciated from the above description, the typical prior art rotors, with large, heavy magnets and a relatively massive support structure, add considerable mass to the engine crank shaft to which the rotor is attached. The result is a relatively large moment of inertia that must be overcome upon starting the engine. Furthermore, the relatively large rotor mass results in inertial losses that impair acceleration.
There has thus been a long-felt need for a magneto rotor of substantially reduced mass that does not sacrifice either structural strength or magnetic field strength.